Protoplanetary Disk Evolution: Singles vs. Binaries

AbstractBased on a large number of observations carried out in the last decade it appears that the fraction of stars with protoplanetary disks declines steadily between ~1 Myr and ~10 Myr. We do, however, know that the multiplicity fraction of star-forming regions can be as high as >50% and that multiples have reduced disk lifetimes on average. As a consequence, the observed roughly exponential disk decay can be fully attributed neither to single nor binary stars and its functional form may need revision. Observational evidence for a non-exponential decay has been provided by Kraus et al. (2012), who statistically correct previous disk frequency measurements for the presence of binaries and find agreement with models that feature a constantly high disk fraction up to ~3 Myr, followed by a rapid (≲2 Myr) decline.We present results from our high angular resolution observational program to study the fraction of protoplanetary disks of single and binary stars separately. We find that disk evolution timescales of stars bound in close binaries (<100 AU) are significantly reduced compared to wider binaries. The frequencies of accretors among single stars and wide binaries appear indistinguishable, and are found to be lower than predicted from planet forming disk models governed by viscous evolution and photoevaporation.

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First Results from ATCA at Millimetre Wavelengths

Symposium - International Astronomical Union ◽

10.1017/s0074180900241685 ◽

2004 ◽

Vol 221 ◽

pp. 275-282

Author(s):

Vincent Minier

Keyword(s):

Star Formation ◽

Angular Resolution ◽

Galactic Plane ◽

Dust Emission ◽

Protoplanetary Disks ◽

High Angular Resolution ◽

Star Forming ◽

Star Forming Regions ◽

First Results ◽

Excellent Tool

The newly upgraded Australia Telescope Compact Array (ATCA) at millimetre wavelengths is the first millimetre interferometer to be built in the Southern Hemisphere. The full array will be operational in 2004-2005 and will provide arcsec angular resolution at 3 mm and 12 mm. This will be a unique instrument to study at high angular resolution the interstellar chemistry and more generally the star formation process, especially in the bulk of the galactic plane and in the Magellanic Clouds. The upgraded ATCA will also be an excellent tool to detect dust emission from nearby protoplanetary disks. In this paper I will present the first results from the upgraded ATCA at 3 mm and 12 mm. The result review will cover the topics of massive star formation and hot molecular cores dust emission from star-forming regions and detection of protoplanetary disks.

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Evolutionary Synthesis Models of Young Star‐forming Regions: The Influence of Binary Stars

The Astrophysical Journal ◽

10.1086/500380 ◽

2006 ◽

Vol 641 (1) ◽

pp. 252-267 ◽

Cited By ~ 14

Author(s):

Dany Dionne ◽

Carmelle Robert

Keyword(s):

Binary Stars ◽

Young Star ◽

Evolutionary Synthesis ◽

Star Forming ◽

Star Forming Regions

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Star Clusters in Irregular Galaxies in the Local Group

Symposium - International Astronomical Union ◽

10.1017/s0074180900223425 ◽

2002 ◽

Vol 207 ◽

pp. 94-104

Author(s):

Eva K. Grebel

Keyword(s):

Globular Clusters ◽

Local Group ◽

Cluster Formation ◽

Star Clusters ◽

Open Clusters ◽

High Angular Resolution ◽

Star Clusters And Associations ◽

Star Forming ◽

Star Forming Regions ◽

Irregular Galaxies

I summarize our knowledge of star clusters and associations in irregular galaxies other than the Magellanic Clouds in the Local Group. Surveys affording complete area coverage at high angular resolution are still lacking. Confirmed globular clusters are known only in NGC 6822 and WLM. Very few dIrrs contain populous or sparse open clusters. There is a pronounced deficiency of intermediate-age and young clusters. Apart from parent galaxy mass, the lack of interactions may be a key reason for the lack of cluster formation in the dIrrs. All dIrrs have one or several short-lived OB associations in the star-forming regions in their centers.

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The Calibration of Interferometrically Determined Properties of Binary Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900078803 ◽

1985 ◽

Vol 111 ◽

pp. 97-119

Author(s):

Harold A. McAlister

Keyword(s):

Binary Stars ◽

Angular Resolution ◽

Binary Star ◽

Angular Separation ◽

Speckle Interferometry ◽

Close Binaries ◽

High Angular Resolution ◽

Fundamental Field ◽

Enhanced Resolution ◽

Stellar Masses

With the advent of speckle interferometry, high angular resolution has begun to play a routine role in the study of binary stars. Speckle and other interferometric techniques not only bring enhanced resolution to this classic and fundamental field but provide an equally important gain in observational accuracy. These methods also offer the potential for performing accurate differential photometry for binary stars of very small angular separation. This paper reviews the achievements of modern interferometric techniques in measuring stellar masses and luminosities and discusses the special calibration problems encountered in binary star interferometry. The future possibilities for very high angular resolution studies of close binaries are also described.

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ALMA survey of Class II protoplanetary disks in Corona Australis: a young region with low disk masses

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935273 ◽

2019 ◽

Vol 626 ◽

pp. A11 ◽

Cited By ~ 16

Author(s):

P. Cazzoletti ◽

C. F. Manara ◽

H. Baobab Liu ◽

E. F. van Dishoeck ◽

S. Facchini ◽

...

Keyword(s):

Angular Momentum ◽

Mass Distribution ◽

Planet Formation ◽

Protoplanetary Disks ◽

Class Ii ◽

Star Forming ◽

Star Forming Regions ◽

Disk Mass ◽

Intrinsic Angular Momentum ◽

Dust Mass

Context. In recent years, the disk populations in a number of young star-forming regions have been surveyed with the Atacama Large Millimeter/submillimeter Array (ALMA). Understanding the disk properties and their correlation with the properties of the central star is critical to understanding planet formation. In particular, a decrease of the average measured disk dust mass with the age of the region has been observed, consistent with grain growth and disk dissipation. Aims. We aim to compare the general properties of disks and their host stars in the nearby (d = 160 pc) Corona Australis (CrA) star forming region to those of the disks and stars in other regions. Methods. We conducted high-sensitivity continuum ALMA observations of 43 Class II young stellar objects in CrA at 1.3 mm (230 GHz). The typical spatial resolution is ~0.3′′. The continuum fluxes are used to estimate the dust masses of the disks, and a survival analysis is performed to estimate the average dust mass. We also obtained new VLT/X-shooter spectra for 12 of the objects in our sample for which spectral type (SpT) information was missing. Results. Twenty-four disks were detected, and stringent limits have been put on the average dust mass of the nondetections. Taking into account the upper limits, the average disk mass in CrA is 6 ± 3 M⊕. This value is significantly lower than that of disks in other young (1–3 Myr) star forming regions (Lupus, Taurus, Chamaeleon I, and Ophiuchus) and appears to be consistent with the average disk mass of the 5–10 Myr-old Upper Sco. The position of the stars in our sample on the Herzsprung-Russel diagram however seems to confirm that CrA has an age similar to Lupus. Neither external photoevaporation nor a lower-than-usual stellar mass distribution can explain the low disk masses. On the other hand, a low-mass disk population could be explained if the disks were small, which could happen if the parent cloud had a low temperature or intrinsic angular momentum, or if the angular momentum of the cloud were removed by some physical mechanism such as magnetic braking. Even in detected disks, none show clear substructures or cavities. Conclusions. Our results suggest that in order to fully explain and understand the dust mass distribution of protoplanetary disks and their evolution, it may also be necessary to take into consideration the initial conditions of star- and disk-formation process. These conditions at the very beginning may potentially vary from region to region, and could play a crucial role in planet formation and evolution.

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A Two-Dimensional Near—Infrared Speckle Imaging Survey of T Tauri Stars in Taurus and Ophiuchus

International Astronomical Union Colloquium ◽

10.1017/s0252921100006059 ◽

1992 ◽

Vol 135 ◽

pp. 1-9

Author(s):

A. Ghez ◽

G. Neugebauer ◽

K. Matthews

Keyword(s):

Binary Stars ◽

Near Infrared ◽

Angular Separation ◽

Speckle Interferometry ◽

T Tauri Stars ◽

Two Dimensional ◽

Star Forming ◽

Double Stars ◽

Star Forming Regions ◽

T Tauri

AbstractWe present the results of a magnitude limited (K≤8.5 mag) multiplicity survey of T Tauri stars in the two nearest star forming regions, Taurus-Auriga and Ophiuchus-Scorpius (D = 150 pc), observable from the northern hemisphere. Each of the 70 stars in the sample was imaged at 2.2 μm using two-dimensional speckle interferometry resulting in a survey sensitive to binary stars with separations ranging from 0.″09 to about 2″.5.The frequency of double stars with separation in this range is 46±8%. A division between the classical T Tauri stars and the weak-lined T Tauri stars shows no distinction. Furthermore, no difference is observed between the binary frequencies in the two star forming regions although the clouds have very different properties.Given the limited angular separation range that this survey is sensitive to, both the spectroscopic and wide binaries will be missed. The rate at which binaries are detected suggests that most, if not all, T Tauri stars have companions.

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Disk Masses and Dust Evolution of Protoplanetary Disks around Brown Dwarfs

The Astrophysical Journal ◽

10.3847/1538-4357/ac09e5 ◽

2021 ◽

Vol 921 (2) ◽

pp. 182

Author(s):

Anneliese M. Rilinger ◽

Catherine C. Espaillat

Keyword(s):

Planet Formation ◽

Spectral Energy ◽

Star Forming ◽

Star Forming Regions ◽

Disk Mass ◽

T Tauri ◽

Multiple Regions ◽

Disk Evolution ◽

Dust Grain ◽

Dust Evolution

Abstract We present the largest sample of brown dwarf (BD) protoplanetary disk spectral energy distributions modeled to date. We compile 49 objects with ALMA observations from four star-forming regions: ρ Ophiuchus, Taurus, Lupus, and Upper Scorpius. Studying multiple regions with various ages enables us to probe disk evolution over time. Specifically, from our models, we obtain values for dust grain sizes, dust settling, and disk mass; we compare how each of these parameters vary between the regions. We find that disk mass decreases with age. We also find evidence of disk evolution (i.e., grain growth and significant dust settling) in all four regions, indicating that planet formation and disk evolution may begin to occur at earlier stages. We generally find that these disks contain too little mass to form planetary companions, though we cannot rule out that planet formation may have already occurred. Finally, we examine the disk mass–host mass relationship and find that BD disks are largely consistent with previously determined relationships for disks around T Tauri stars.

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ALMA observations of water deuteration: a physical diagnostic of the formation of protostars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936012 ◽

2019 ◽

Vol 631 ◽

pp. A25 ◽

Cited By ~ 2

Author(s):

S. S. Jensen ◽

J. K. Jørgensen ◽

L. E. Kristensen ◽

K. Furuya ◽

A. Coutens ◽

...

Keyword(s):

Signal To Noise Ratio ◽

High Angular Resolution ◽

Cloud Environment ◽

Star Forming ◽

Star Forming Regions ◽

Cloud Dynamics ◽

Solar System Bodies ◽

History Of ◽

Low Mass ◽

Local Cloud

Context. How water is delivered to planetary systems is a central question in astrochemistry. The deuterium fractionation of water can serve as a tracer for the chemical and physical evolution of water during star formation and can constrain the origin of water in Solar System bodies. Aims. The aim is to determine the HDO/H2O ratio in the inner warm gas toward three low-mass Class 0 protostars selected to be in isolated cores, i.e., not associated with any cloud complexes. Previous sources for which the HDO/H2O ratio have been established were all part of larger star-forming complexes. Determining the HDO/H2O ratio toward three isolated protostars allows comparison of the water chemistry in isolated and clustered regions to determine the influence of local cloud environment. Methods. We present ALMA Band 6 observations of the HDO 31,2–22,1 and 21,1–21,2 transitions at 225.897 GHz and 241.562 GHz along with the first ALMA Band 5 observations of the H218O 31,3–22,0 transition at 203.407 GHz. The high angular resolution observations (0′′.3–1′′.3) allow the study of the inner warm envelope gas. Model-independent estimates for the HDO/H2O ratios are obtained and compared with previous determinations of the HDO/H2O ratio in the warm gas toward low-mass protostars. Results. We successfully detect the targeted water transitions toward the three sources with signal-to-noise ratio (S/N) > 5. We determine the HDO/H2O ratio toward L483, B335 and BHR71–IRS1 to be (2.2 ± 0.4) × 10−3, (1.7 ± 0.3) × 10−3, and (1.8 ± 0.4) × 10−3, respectively, assuming Tex = 124 K. The degree of water deuteration of these isolated protostars are a factor of 2–4 higher relative to Class 0 protostars that are members of known nearby clustered star-forming regions. Conclusions. The results indicate that the water deuterium fractionation is influenced by the local cloud environment. This effect can be explained by variations in either collapse timescales or temperatures, which depends on local cloud dynamics and could provide a new method to decipher the history of young stars.

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Dust Trapping and Coagulation in Protoplanetary Disks

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319002011 ◽

2018 ◽

Vol 14 (S345) ◽

pp. 355-357

Author(s):

Ya-Ping Li

Keyword(s):

Protoplanetary Disks ◽

Large Family ◽

Continuum Emission ◽

Nearby Star ◽

Dust Trapping ◽

Star Forming ◽

Star Forming Regions ◽

Hydrodynamical Simulations ◽

Two Fluid ◽

Key Parameter

AbstractIn this work, we carry out two-fluid (gas+dust) hydrodynamical simulations on a large family of models in order to study the dust coagulation and the dust-gas dynamical processes in protoplanetary disks. Our theoretical effort is guided by the observational results of disks in nearby star forming regions at sub-millimeter and millimeter (mm) wavelengths. By a systematic comparison with the continuum emission at several mm bands from ALMA observations, we find that ringed structures are predicated in the unresolved faint disks for those with mm spectral indexes as low as about 2.0. Our parameter exploration can also be used to constrain the fragmentation velocity, one key parameter of the dust coagulation model, and some other disk parameters.

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